1. Field of the Invention
The claimed invention relates to a coating apparatus and an inkjet recording apparatus. In particular, the claimed invention relates to a coating apparatus and an inkjet recording apparatus, in which coating liquid is applied by roller coating.
2. Description of the Related Art
In the past, a printing system that performs image formation by ink jetting onto general-purpose paper has been proposed. In such a printing system, treatment liquid that causes an aggregation reaction of ink is applied onto paper in advance prior to inkjet dropping. As means for applying the treatment liquid, a dropping method by an inkjet head or various methods such as a die coater, a slit coater, and a curtain coater which are traditional coating methods have been considered. However, as a method in which a high-quality coated surface is obtained at a relatively low price and stably, a roller coating method is used.
Among them, in an inkjet system which uses a sheet transport drum method, a method is known which performs on-demand coating by having an anilox roller (a measuring roller) contact with and separate from a coating roller for each sheet of paper in order to prevent extra coating liquid from sticking to areas other than the paper.
Here, the anilox roller is immersed in a coating liquid pan and draws up the coating liquid therefrom. Then, a measuring blade scraps away extra coating liquid from the anilox roller, and thereby a certain amount of liquid is supplied to the coating roller. However, in a case where a non-application state (a standby state or the like of a device) lasts for a long time, there is a problem in that a solvent of the coating liquid in the coating liquid pan evaporates due to the circulation of liquid, whereby the coating liquid is concentrated, and thus image quality deteriorates. For this reason, control is required which detects the concentration of the coating liquid and maintains a constant concentration of the coating liquid by supplying diluting liquid in a case of a certain threshold being exceeded. However, in this case, since a concentration meter, a diluting liquid tank, piping for dilution, a pump, a flow path valve, or the like is additionally required. Accordingly, there is also a problem in that the cost of a device increases and labor of a user such as diluting liquid replenishment work or regular cleaning of the concentration meter increases.
In order to solve such problems, for example, in JP2012-56261A, there is described a configuration in which in a coating device using a squeeze roller and a coating roller, the entirety of the squeeze roller and the coating roller is covered by a housing member. Further, in JP2007-296424A, there is described a coating device in which for evaporation prevention, a roller and a base material are covered by a cover and when the roller is retreated at the time of non-coating, the cover is also simultaneously moved. Further, in JP2009-172506A, there is disclosed a coating device configured so that a hermetically-sealed liquid retaining section is brought into contact with a roller.